CVE-2026-8391: Other issue in the JavaScript Engine component

Published May 12, 2026
·
Updated

Other issue in the JavaScript Engine component. This vulnerability was fixed in Firefox 150.0.3, Firefox ESR 115.36, Firefox ESR 140.11, and Thunderbird 140.11.

Affected Software

6 affected componentsFixes available
Mozilla Firefox<150.0.3
Mozilla Firefox<150.0.3
150.0.3
Mozilla Firefox ESR<115.36
115.36
Mozilla Firefox ESR<140.11
140.11
Mozilla Firefox<150.0.3
Mozilla Thunderbird<140.11
140.11

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 150.0.3
  2. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 115.36
  3. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 140.11
  4. Upgrade

    Upgrade Mozilla Firefox to a version that resolves this vulnerability.

    Fixed in 150.0.3
  5. Upgrade

    Upgrade Firefox ESR to a version that resolves this vulnerability.

    Fixed in 115.36
  6. Upgrade

    Upgrade Firefox ESR to a version that resolves this vulnerability.

    Fixed in 140.11
  7. Upgrade

    Upgrade Mozilla Thunderbird to a version that resolves this vulnerability.

    Fixed in 140.11

Event History

May 12, 2026
CVE Published
via Mozilla·12:00 AM
Data Sourced
via Mozilla·12:00 AM
DescriptionSeverityAffected Software
CVE Published
via MITRE·12:36 PM
Data Sourced
via MITRE·12:36 PM
Description
Data Sourced
via Red Hat·02:02 PM
DescriptionSeverityAffected Software
Data Sourced
via NVD·02:17 PM
DescriptionSeverityWeaknessAffected Software
May 19, 2026
Updated
via Mozilla·12:00 AM
Affected Software
Jan 24, 58467
Event
via NVD·02:26 PM

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

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Frequently Asked Questions

1

What is the severity of CVE-2026-8391?

CVE-2026-8391 is considered to be a high severity vulnerability due to its potential impact on the JavaScript Engine in Mozilla Firefox.

2

How do I fix CVE-2026-8391?

To fix CVE-2026-8391, users should update Mozilla Firefox to version 150.0.3 or later.

3

What components are affected by CVE-2026-8391?

CVE-2026-8391 affects the JavaScript Engine component of Mozilla Firefox.

4

Was CVE-2026-8391 exploited in the wild?

There is no public information indicating that CVE-2026-8391 has been exploited in the wild.

5

What versions of Firefox are vulnerable to CVE-2026-8391?

Firefox versions prior to 150.0.3 are vulnerable to CVE-2026-8391.

Company

Resources

Contact

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